Olefin polymer films

ABSTRACT

Disclosed are films or sheets comprising a blend of 1) a heterophasic olefin polymer composition and 2) a copolymer of ethylene with a CH 2  ═CHR alpha-olefin, where R is a C 1-8  straight or branched alkyl. 
     Coextruded films or sheets and laminates wherein at least one layer is a film or sheet as described above, and films or sheets of blends of the olefin polymer composition and another olefin polymer are also disclosed.

FIELD OF THE INVENTION

This invention relates to thermoplastic films, sheets and laminates andcoextruded materials formed therefrom, and films and sheets formed fromblends of an olefin polymer composition applied to a base film or sheetof a metallic substrate or of different olefin polymer materials.

BACKGROUND OF THE INVENTION

In many film applications, such as packaging of foodstuffs, chemical andhazardous materials and in medical applications, the industry requiresfilms having certain properties. In the packaging of foodstuffs, forexample, the films must have high puncture resistance, high clarity andgloss, and reduced permeability to gases and/or vapors. The films usedto manufacture containers for chemicals and hazardous waste materialsmust have a high puncture resistance, high elongation strength, hightear resistance and chemical resistance. Films used in medicalapplications, such as blood bags, must have a high puncture resistance,low modulus, high tear resistance and auto-clavability.

Thus, there is a need for a polymer material which has a lower flexuralmodulus, good tear strength, higher elastic recovery, reduced drawresonance, as well as all of the other desirable properties.

Films made from ethylene polymers, homopolymers, e.g., HDPE and LLDPE,and copolymers, e.g., LLDPE, and propylene polymers, such as crystallinehomopolymers of propylene and random copolymers of propylene andethylene, do not provide such a combination of desirable properties.

Attempts have been made to overcome the shortcomings of these polymersby preparing heterophasic mixtures of crystalline propylene polymers and8 to 25% of an elastomeric propylene-ethylene copolymer by sequentialpolymerization in the presence of a stereospecific Ziegler-Natta typecatalyst. However, films of such heterophasic compositions are subjectto the formation of fisheyes, inadequate tear strength or the formationof rough surfaces.

SUMMARY OF THE INVENTION

It has now been found that compositions having low modulus, good tearstrength, higher elastic recovery, reduced draw resonance, and retentionof all of the other desirable properties can be obtained by blendingethylene copolymers with a heterophasic olefin polymer composition.

Accordingly, this invention provides a thermoplastic film having thedesired properties comprising a blend of 1) a heterophasic olefinpolymer composition which is comprised of:

(a) from about 10 to 50 parts of a propylene homopolymer having anisotactic index greater than 80, or a copolymer selected from the groupconsisting of (i) propylene and ethylene, (ii) propylene, ethylene and aCH₂ ═CHR alpha-olefin, where R is a C₂₋₈ straight or branched alkyl, and(iii) propylene and an alpha-olefin as defined in (a) (ii), saidcopolymer containing over propylene and having an isotactic indexgreater than 80;

(b) from about 5 to 20 parts of a semi-crystalline, essentially linearcopolymer fraction having a crystallinity of about 20 to 60%, whereinthe copolymer is selected from the group consisting of (i) ethylene andpropylene containing over 55% ethylene, (ii) ethylene, propylene, and analpha-olefin as defined in (a) (ii) containing from 1 to 10% of thealpha-olefin and over 55% of both ethylene and alpha-olefin, and (iii)ethylene and an alpha-olefin as defined in (a) (ii) containing over 55%of said alpha-olefin, which copolymer is insoluble in xylene at room orambient temperature; and

(c) from about 40 to 80 parts of a copolymer fraction is selected fromthe group consisting of a copolymer of (i) ethylene and propylenewherein the copolymer contains from 20% to less than 40% ethylene and,(ii) ethylene, propylene, and an alpha-olefin as defined in (a) (ii)wherein the alpha-olefin is present in an amount of 1 to 10% and theamount of ethylene and alpha-olefin present is from 20% to less than40%, and (iii) ethylene and an alpha-olefin as defined in (a) (ii)containing from 20% to less than 40% of the alpha-olefin, and optionallywith 0.5 to 10% of a diene, said copolymer fraction being soluble inxylene at ambient temperature, and having an intrinsic viscosity of from1.5 to 4.0 dl/g;

with the total of the (b) and (c) fractions, based on the total olefinpolymer composition, being from about 50% to 90%, and the weight ratioof (b)/(c) being less than 0.4; and

2) a copolymer of ethylene with a CH₂ ═CHR alpha-olefin, where R is aC₁₋₈ straight or branched alkyl, having a density of 0.875 g/cm³ orgreater.

In another embodiment this invention provides films comprising a layerof the blend of this invention applied to at least one surface of athermoplastic film or a nonwoven material or a metallic substrate.

The films made from the blends of the present invention can be used indiapers, especially diaper cover stocks, especially bonded to scrim. Ingeneral, films from the blend of the invention can be used in personalcare products, e.g. diapers and pull-ups; adult incontinence; disposablemedical wear, such as gowns; shoe fascias; and feminine hygieneproducts.

DETAILED DESCRIPTION OF THE INVENTION

All parts and percentages used in this application are by weight unlessotherwise specified. Ambient or room temperature is approximately 25° C.

Component 1) (a) is preferably present in an amount from 10 to 40 parts,most preferably from 20 to 35 parts. When (a)is a propylene homopolymer,the isotactic index is preferably from about 85 to 98. When (a) is acopolymer, the amount of propylene in the copolymer is preferably fromabout 90 to 99%.

Component 1) (b) is preferably present in an amount from 7 to 15 parts.Typically the crystallinity is about 20 to 60% by differential scanningcalorimetry (DSC). Generally, the ethylene or said alpha-olefin contentor the combination of ethylene and said alpha-olefin when both are usedis over 55% up to 98%, preferably from 80 to 95%.

Component 1) (c) is preferably present in an amount from 50 to 70 parts.The ethylene or said alpha-olefin content or ethylene and saidalpha-olefin content of component (c) is preferably from 20 to 38%, mostpreferably from 25 to 38%. When component (c) is a terpolymer, the saidalpha-olefin is typically present in an amount from 1 to 10%, preferably1 to 5%. The preferred intrinsic viscosity is from 1.7 to 3 dl/g.

The total amount of 1) (b) and (c), based on the total olefin polymercomposition is preferably from 65 to 80% and the weight ratio of (b)/(c)is preferably from 0.1 to about 0.3.

The total amount of ethylene units or said alpha-olefin units, or ofethylene and said alpha-olefin units when both are present, incomponent 1) of the blend of this invention is from about 15% to about35%.

in addition, the compositions of component 1) have a flexural modulus ofless than 150 MPa, generally from 20 and 100 MPa; a tensile strength atyield of from 10 to 20 MPa, elongation at break over 400%; a tensionset, at 75% strain, from 20% to 50%; a Shore D hardness from 20 and 35;and do not break (no brittle impact failure) when an IZOD impact test isconducted at -50° C.

Component 2) is a copolymer of ethylene with a CH₂ ═CHR alpha-olefin,where R is a C₁₋₈, preferably a C₂₋₆, and most preferably a C₄₋₆straight or branched alkyl. The alpha-olefin is present in an amountfrom about 1 to 10% and preferably from 6-10%. Suitable ethylenecopolymers useful as component 2) include ethylene/butene-1,ethylene/4-methyl-1-pentene, ethylene/hexene-1 and ethylene/octene-1.The copolymer can be a LLDPE, or VLDPE, preferably an LLDPE, where thecomohomer is 1-octerie. Preferably the density of the ethylene copolymeris 0.089 to 0.940 g/cm³, and most preferably from 0.890 to 0.927 g/cm³.

The blends of the present invention contain from 60 to 95%, by weight,of component 1) and from 5 to 40%, by weight, of component 2).Preferably, component 1) is present in an amount of from 90 to 75% andcomponent 2) is present in an amount of from 10 to 25%.

The blends of this invention have at least one melt peak, determined byDSC, present at temperatures higher than 120° C., and at least one peak,relative to the vitreous transition, present at temperatures from -10° Cand -35° C.

Typically, the blends of the present invention have a flexural modulusof less than 150 MPa, generally from 20 to 100 MPa.

Copolymer and terpolymers of propylene and ethylene or an alpha-olefinor of propylene, ethylene and an alpha-olefin are preferred ascomponent 1) (a), and copolymers of propylene with ethylene or analpha-olefin are most preferred as component (a).

Suitable alpha-olefins of the formula CH₂ ═CHR include butene-1,pentene-1, 4-methylpentene-1, hexene-1, and octene-1. When used toprepare component 1) (a) they are present in such quantities that theisotactic index of the resulting polymer is not less than 80%.

When a diene is present during the preparation of components 1) (b) and(c), it is typically a butadiene, 1,4-hexadiene, 1,5-hexadiene,ethylidene norbornene diene monomer and is typically present in amountfrom 0 5 to 10% preferably 1 to 5%.

The component 1) can be prepared with a polymerization processcomprising at least two stages, where in the first stage the propyleneor propylene and ethylene or said alpha-olefin or propylene, ethylene orsaid alpha-olefin are polymerized to form component 1) (a), and in thefollowing stages the mixtures ethylene and propylene or saidalpha-olefin or ethylene, propylene and said alpha-olefin, andoptionally a diene, are polymerized to form components i) (b) and (c).

The polymerization can be conducted in liquid phase, gas phase, orliquid-gas phase using separate reactors, all of which can be doneeither by batch or continuously. For example, it is possible to carryout the polymerization of component 1) (a) using liquid propylene asdiluent, and the polymerization of components 1) (b) and (c) in gasphase without intermediate stages except for the partial degassing ofthe propylene. This is the preferred method.

The polymerization reactions are carried out in an inert atmosphere inthe presence of an inert hydrocarbon solvent or of a liquid or gaseousmonomer.

Suitable inert hydrocarbon solvents include saturated hydrocarbons, suchas propane, butane, hexane and heptane.

Hydrogen can be added as needed as a chain transfer agent for control ofthe molecular weight.

The reaction temperature in the polymerization of component 1) (a) andfor the polymerization of components 1) (b) and (c), can be the same ordifferent, and is generally from 40° C. to 90° C., preferably 50° to 80°C. for the polymerization of component 1) (a), and 40° to 65° C. for thepolymerization of components 1) (b) and (c).

The pressure of the polymerization of component i) (a), if carried outin liquid monomer, is the one which competes with the vapor pressure ofthe liquid propylene at the operating temperature used, eventuallymodified by the vapor pressure of the small quantity of inert diluentused to feed the catalyst mixture, and the overpressure of optionalmonomers and the hydrogen used as molecular weight regulator.

The pressure of the polymerization of components 1) (b) and (c), if donein gas phase, can be from 5 to 30 arm. The residence times relative tothe two stages depend on the desired ratio between fraction (a) and(b)+(c), and are usually from 15 min. to 8 hours.

The catalyst used in the polymerization comprises the reaction productof 1) a solid component containing a halogen-containing titaniumcompound and an electron-donor compound (internal donor) supported on anactivated magnesium chloride, 2) a non-halogen containing Al-trialkylcompound and 3) an electron-donor compound (external donor).

Suitable titanium compounds include those with at least one Ti-halogenbond, such as halides and alkoxy halides of titanium.

In order to obtain these olefin polymer compositions in the form offlowable spherical particles having a high bulk density, the solidcatalyst component must have a) a surface area smaller than 100 m² /g,preferably between 50 and 80 m² /g, b) a porosity from 0.25 to 0.4 cc/g.and c) an X-ray spectrum, where the magnesium chloride reflectionsappear, showing the presence of a halo between the angles 2σ of 33.5°and 35° and by the absence of the reflection at 22σ of 14.95°. Thesymbol σ=Bragg angle.

The solid catalyst component is prepared by forming an adduct ofmagnesium dichloride and an alcohol, such as ethanol, propanol, butanoland 2-ethylhexanol, containing generally 3 moles of alcohol per mole ofMgCl₂, emulsifying the adduct, cooling the emulsion quickly to cause theadduct to solidify into spherical particles, and partiallydealcoholating the particulate adduct by gradually increasing thetemperature from 50° C. to 130° C. for a period of time sufficient toreduce the alcohol content from 3 moles to 1-1.5 moles per mole ofMgCl₂. The partially dealcoholated adduct is then suspended in TiCl₄ at0° C., such that the concentration of adduct to TiCl₄ is 40-50 g/lTiCl₄. The mixture is then heated to a temperature of 80° C. to 135° C.for a period of about 1-2 hr. When the temperature reaches 40° C.,sufficient electron donor is added so that the desired molar ratio of Mgto electron donor is obtained.

An electron-donor compound selected preferably among the alkyl,cycloalkyl, and aryl phthalates, such as for example diisobutyl,di-n-butyl, and di-n-octyl phthalate, is added to the TiCl₄.

When the heat treatment period has ended, the excess hot TiCl₄ isseparated by filtration or sedimentation, and the treatment with TiCl₄is repeated one or more times. The solid is then washed with a suitableinert hydrocarbon compound, such as hexane or heptane, and dried.

The solid catalyst component typically has the followingcharacteristics:

Surface area: less than 100 m² /g, preferably between 50 and 80 m² /g

Porosity: 0.25-0.4 cc/g

Pore volume distribution: 50% of the pores have a radius greater than100 angstroms.

X-ray spectrum: where the Mg chloride reflections appear, showing a halowith maximum intensity between angles of 2σ of 33.5° and 35° and wherethe reflection of 2σ of 14.95° is absent.

The catalyst is obtained by mixing the solid catalyst component with atrialkyl aluminum compound, preferably triethyl aluminum and triisobutylaluminum, and an electron-donor compound.

Various electron donor compounds are known in the art. The preferredelectron donor compounds are those silane compounds having the formulaR'R"Si(OR)₂ where R' and R" may be the same or different and are C₁₋₁₈normal or branched alkyl, C₅₋₁₈ cycloalkyl, or C₆₋₁₈ aryl radicals, andR is a C₁₋₄ alkyl radical.

Typical silane compounds which may be used includediphenyldimethoxysilane, dicyclohexyldimethoxysilane,methyl-t-butyldimethoxysilane, diisopropyldimethoxysilane,dicyclopentyldimethoxysilane, cyclohexylmethyldimethoxysilane andphenyltrimethoxysilane.

The Al/Ti ratio is typically between 10 and 200 and the Al/silane molarratio between 1/1 and 1/100.

The catalysts may be precontacted with small quantities of olefinmonomer (prepolymerization), maintaining the catalyst in suspension in ahydrocarbon solvent and polymerizing at atemperature from roomtemperature to 60° C. for a time sufficient to produce a quantity ofpolymer from 0.5 to 3 times the weight of the catalyst.

This prepolymerization also can be done in liquid or gaseous monomer toproduce, in this case, a quantity of polymer up to 1000 times thecatalyst weight.

The content and amount of catalyst residue in the thermoplastic olefinpolymers of this invention is sufficiently small so as to make theremoval of catalyst residue, typically referred to as deashing,unnecessary.

The heterophasic olefin polymer, component 1), prepared with theaforementioned catalyst are in spheroidal particle form, and theparticles have a diameter from 0.5 to 7 mm.

The heterophasic olefin polymer used in the blends of this invention canbe a "visbroken" polymer prepared from spherical particles as describedabove, having a melt flow rate (MFR, according to ASTM D-1238, measuredat 230° C., 2.16 kg) of from 5 to 400, preferably from 10 to 200, andmost preferably from 20 to 100, from an initial MFR of from 0.2 to 20,and preferably about 0.5 to 3.

Alternatively, component 1) can be produced directly in thepolymerization reactor to the preferred MFR.

The process of visbreaking component 1) is well known in the art.Generally, it is carried out as follows: heterophasic olefin polymermaterial in "as polymerized" form, e.g., flaked, powders or spheres outof the polymerization reactor or pelletized, has sprayed thereon orblended therewith, a prodegradant or free radical generating source,e.g., a peroxide in liquid or powder form or a peroxide/polypropyleneconcentrate, such as Xantrix 3024 peroxide concentrate available fromHIMONT U.S.A., Inc. The heterophasic olefin polymer material andperoxide is then introduced into means for thermally plasticizing andconveying the mixture, e.g., an extruder at elevated temperature.Residence time and temperature are controlled in relation to theparticular peroxide selected (i.e., based on the half-life of theperoxide at the process temperature of the extruder) so as to effect thedesired degree of polymer chain degradation. The net result is to narrowthe molecular weight distribution of the polymer as well as to reducethe overall molecular weight and thereby increase the MFR relative tothe as-polymerized polymer. For example, a polymer with a fractional MFR(i.e., less than 1), or a polymer with a MFR of 0.5 to 10, can beselectively visbroken to a MFR of 15 to 50, preferably 28 to 42, byselection of peroxide type, extruder temperature and extruder residencetime without undue experimentation. Sufficient care should be exercisedin the practice of the procedure to avoid crosslinking in the presenceof an ethylene-containing copolymer; typically, crosslinking can beeasily avoided where the ethylene content of the copolymer issufficiently low.

The rate of peroxide decomposition is defined in terms of half-lives,i.e., the time required at a given temperature for one-half of theperoxide molecules to decompose. It has been reported (U.S. Pat. No.4,451,589) for example, that using Lupersol 101 peroxide under typicalextruder pelletizing conditions (450° F., 21/2 minutes residence time),only 2×10⁻¹³ % of the peroxide would survive pelletizing.

In general, the prodegradant should not interfere with or be adverselyaffected by commonly used polypropylene stabilizers and shouldeffectively produce free radicals that upon decomposition initiatedegradation of the polypropylene moiety. The prodegradant should have ashort enough half-life at a polymer manufacturing extrusiontemperatures, however, so as to be essentially entirely reacted beforeexiting the extruder. Preferably, they have a half-life in thepolypropylene of less than 9 seconds at 550° F. so that at least 99% ofthe prodegradant reacts in the molten polymer before 1 minute ofextruder residence time. Such prodegradants include, by way of exampleand not limitation, the following: 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane-3 and 4-methyl-4-t-butylperoxy-2-pentanone (e.g. Lupersol 130 andLupersol 120 peroxides available from Lucidol Division PenwaltCorporation);3,6,6,9,9-pentamethyl-3-(ethylacetate)-1,2,4,5-tetraoxycyclononane(e.g., USP-138 peroxide from Witco Chemical Corporation); and1,1'-bis(tert-butylperoxy) diisopropylbenzene (e.g., Vulcup R peroxidefrom Hercules Incorporated). Preferred concentration of the free radicalsource prodegradants are in the range of from about 0.01 to 0.4 percentbased on the weight of the polymer. Particularly preferred is Luperol101 peroxide.

The blends of the invention can be prepared by mechanically blendingcomponent 1) and component 2) by conventional mixing processes, inconventional compounding equipment.

Analytical Methods

Unless otherwise specified, the following analytical methods are used tocharacterize the supported catalyst component, the heterophasic olefinpolymer compositions, films prepared therefrom and comparative filmmaterials.

    ______________________________________                                        Properties     Method                                                         ______________________________________                                        Melt Flow Rate, g/10 min.                                                                    ASTM-D 1238, condition L                                       Ethylene, wt % I. R. Spectroscopy                                             Intrinsic viscosity                                                                          Determined in tetrahydro-                                                     naphthalene at 135° C.                                  Xylene solubles, wt %                                                                        See description below.                                         Flexural modulus at 23° C.                                                            Using a device for dynamic-                                    and Vitreous transition                                                                      mechanical measurements of                                     temperature    DMTA of Polymer Laboratories at a                                             frequency measure of 1 H.sub.2 and                                            a scanning temperature of 2° C./min.                                   A sample plaque (40 × 10 × 2 mm) of the                           polymer to be analyzed is cut from                                            a pressure molded sheet prepared                                              with a Carver press at 200° C. with                                    10 tons of pressure for 10 minutes                                            and then cooling the sheet at                                                 15° C./min.                                             Tension set at 75%                                                                           ASTM-D 412                                                     Tensile Strength at yield                                                                    ASTM-D 638                                                     and at break                                                                  Elongation at yield and                                                                      ASTM-D 638                                                     at break                                                                      Surface area   B.E.T.                                                         Porosity       B.E.T.                                                         Bulk density   DIN-53194                                                      Elemendorf tear                                                                              ASTM-D 1922-78                                                 Dart impact strength                                                                         ASTM D 4272-83                                                 ______________________________________                                    

Unless otherwise specified, the compositions of the present inventionare produced by a general procedure comprising tumble blending component1), which has been visbroken with Lupersol 101,2,5-dimethyl-2,5-bis(t-butylperoxy) hexane, and component 2) set forthbelow in the Examples. Samples of the blend to be subjected to thevarious physical-mechanical analyses are molded by use of a Negri &Bossi 90 injection press, after stabilizing the material with 0.05 pphCyanox 1790 and 0.05 pph calcium stearate, and pelletizing it with asingle screw Bandera extruder (cylinder diameter 30 mm) at 210° C. Theanalytical conditions are as follows:

temperature of the melt 250° C.

temperature of the mold 60° C.

injection time 20 sec.

cooling time 25 sec.

The samples of the film materials were 0.8 to 2.2 mil in thickness andwere cut from the film sheet in the size provided in the particular ASTMtest method being used.

The weight percentage of the sum of the components 1) (b) and (c)fractions, indicated by % (b)+(c), is calculated by determining theweight of the mixture fed during the second stage, and comparing it withthe weight of the final product.

The weight percentage (%) of the components 1) (a), (b), and (c)fractions described herein are determined as follows:

% (a)=100%-[(b)+(c)]

% (c)=S_(f) --P_(a) S_(a)

where S_(f) and S_(a) are the percentage by weight of the portionsoluble in xylene of the final product and the polypropylene fraction(a), respectively; P_(a) is the weight ratio between said fraction andthe final product.

% (b)=100-% (a)-% (c)

The percentage by weight of ethylene or said alpha-olefin or ethyleneand said alpha-olefin contained in copolymer fraction component 1) (c)soluble in xylene is calculated using the following formula: ##EQU1##where: C_(f) =% ethylene and/or said alpha-olefin in the xylene solublesof the final product;

C_(a) =% ethylene and/or said alpha-olefin in the xylene solubles offraction (a);

    X=S.sub.z ·P.sub.a /S.sub.f

The intrinsic viscosity of fraction 1) (c), (I.V..sub.(c)), iscalculated using the following formula:

    (I.V..sub.(c))=(I.V..sub.Sf -I.V..sub.(a).X)/(1-X)

where I.V._(Sf) is the intrinsic viscosity of the xylene solublefraction of the final composition and I.V..sub.(a) is the intrinsicviscosity of the xylene soluble portion of component 1) (a) fraction.

The weight percent of component 1) soluble in xylene at room temperatureis determined by dissolving 2.5 g of the polymer in 250 ml of xylene ina vessel equipped with a stirrer which is heated at 135° C. withagitation for 20 minutes. The solution is cooled to 25° C. whilecontinuing the agitation, and then left to stand without agitation for30 minutes so that the solids can settle. The solids are filtered withfilter paper, the remaining solution is evaporated by treating it with anitrogen stream, and the solid residue is vacuum dried at 80° C. until aconstant weight is reached. The percent by weight of polymer insolublein xylene at room temperature is the isotactic index of the polymer. Thevalue obtained in this manner corresponds substantially to the isotacticindex determined via extraction with boiling n-heptane, which bydefinition constitutes the isotactic index of the polymer.

Examples illustrative of the component 1), physical properties thereof,a process for preparing same, a film based on blends of saidcomponent 1) and component 2) and a method of preparing said film areset forth below.

Solid Catalyst Component A) Preparation of MgCl₂ /Alcohol Adduct

Under an inert atmosphere, 28.4 g anhydrous MgCl₂, 49.5 g of ananhydrous ethanol, 100 ml of ROL OB/30 vaseline oil and 100 ml ofsilicone oil having a viscosity of 350 cs are introduced into a reactionvessel equipped with a stirrer and heated at 120° C. with an oil bathand stirred until the MgCl₂ is dissolved. The hot reaction mixture isthen transferred under inert atmosphere to a 1500 ml vessel equippedwith an Ultra Turrax T-45 N stirrer and a heating jacket and containing150 ml of vaseline oil and 150 ml of silicone oil. The temperature ismaintained at 120° C. with stirring for 3 minutes at 3,000 rpm. Themixture is then discharged into a 2 liter vessel equipped with a stirrercontaining 1,000 ml of anhydrous n-heptane cooled at 0° C. with a dryice/isopar bath and stirred at a tip speed of 6 m/see for about 20minutes while maintaining the temperature at 0° C. The adduct particlesthus formed are recovered by filtering, are washed 3 times at roomtemperature with 500 ml aliquots of anhydrous hexane and graduallyheated by increasing the temperature from 50° C. to 100° C. undernitrogen for a period of time sufficient to reduce the alcohol contentfrom 3 moles to 1.5 moles per mole of MgCl₂. The adduct has a surfacearea of 9.1 m² /g and a bulk density of 0.564 g/cc.

B) Solid Catalyst Component Preparation

The adduct (25 g) is transferred under nitrogen into a reaction vesselequipped with a stirrer and containing 625 ml of TiCl₄ at 0° C. underagitation. It is then heated to 100° C. in 1 hr. When the temperaturereaches 40° C., diisobutylphthalate is added in an amount such that themolar ratio of Mg to diisobutylphthalate is 8. The contents of thevessel are heated at 100° C. for 2 hours with agitation, the agitationis stopped and the solids are allowed to settle. The hot liquid isremoved by siphon.

550 ml of TiCl₄ is added to the solids in the vessel and the mixtureheated at 120° C. for 1 hr. with agitation. The agitation is stopped andthe solids are allowed to settle. The hot liquid is then removed bysiphon. The solids are washed 6 times at 60° C. with 200 ml aliquots ofanhydrous hexane, and then 3 times at room temperature. The solids,after being vacuum dried, have a porosity of 0.261 cc/g, a surface areaof 66.5 m² /g and a bulk density of 0.44 g/cc.

EXAMPLES 1-3

These examples illustrate the heterophasic olefin polymer compositionand amethod for preparing the polymers.

General Operating Conditions

The polymerization runs are conducted under nitrogen in a 22 literstainless steel autoclave equipped with a helicoid magnetic stirrer andoperated at about 90 rpm.

All temperatures, pressures and concentrations of olefin monomers andhydrogen, when present, are constant unless otherwise indicated. Theconcentration of hydrogen and of the relative monomers is analyzedcontinuously in gas phase with a process gas chromatograph and fed inorder to maintain constant the desired concentration of same.

The polymerization is a batch process conducted in two stages. The firststage comprising the polymerization of the relevant monomer or monomersinliquid propylene and the second stage the copolymerization of ethyleneand propylene in gas phase.

In the first stage, the following ingredients in the order in which theyare listed are fed into the autoclave at 20° C. over a period of about10 minutes: 16 1 of liquid propylene, appropriate quantities of ethyleneand hydrogen, and the catalyst system consisting of 1) the solidcatalyst component (about 0.15g) prepared as described above, and 2) amixture of 75 ml of triethyl aluminum (TEAL) at a 10% concentration inhexane and an appropriate quantity of cyclohexylmethyldimethoxysilane(CMMS) electron donor such that the Al/CMMS molar ratio is 7.5. Thecatalyst system is pressure fed into the autoclave with propylene.

The temperature is brought to the desired level in about 10 minutes andmaintained constant throughout the entire polymerization reactionperiod. After the established reaction time has passed, essentially allof the unreacted monomer(s) is/are eliminated by degassing at 60° C. atessentially atmospheric pressure.

In the second stage, the polymer product (a) of the first stage, aftertaking a sample for the various analyses, is brought to the establishedtemperature for the second stage. Propylene and ethylene are then fedintothe autoclave at the ratio and in the quantities established inorder to achieve the pressure and the gas phase composition desired.During the polymerization the pressure and gas phase composition aremaintained by feeding the propylene and ethylene mixture established byway of instruments which regulate or measure or both regulate andmeasure the flow rate. The length of the feed varied according to thecatalyst system employed and the amount of components 1) b) and c)desired in the particular heterophasic olefin polymer product.

At the end of the second stage polymerization reaction the powder isdischarged, stabilized and then oven dried under a nitrogen stream at60° C.

The ingredients and relative operating conditions are set forth in TableIAand the tests results are set forth in Table IB.

                  TABLE 1A                                                        ______________________________________                                        Examples        1         2       3                                           ______________________________________                                        1st Phase                                                                     Temperature, °C.                                                                       70        70      70                                          Pressure, atm.  31        31      31                                          Time, min.      30        20      30                                          H.sub.2 in gas phase, mol %                                                                   0.58      0.10    0.30                                        Ethylene in gas 1.45      2.60    2.50                                        phase, mol %                                                                  Ethylene in pol., wt. %                                                                       3.0       4.3     4.1                                         Intrinsic Visc., dl/g                                                                         2.18      3.09    2.31                                        Xylene Sol. (S.sub.a), wt. %                                                                  9.4       9.0     0.7                                         Ethylene in Xylene Sol.                                                                       11        16      17                                          (C.sub.a), wt. %                                                              Intrinsic Visc. Xylene                                                                        1.15      1.39    1.19                                        Sol. (I.V..sub.a), dl/g                                                       2nd Phase                                                                     Temperature, °C.                                                                       50        50      50                                          Pressure, atm.  11.3      11.5    11.3                                        Time, min.      335       500     250                                         H.sub.2 in gas phase, mol %                                                                   2.23      3.0     2.05                                        Ethylene in gas phase,                                                                        15.9      16.9    22.54                                       mol %                                                                         ______________________________________                                    

                  TABLE 1B                                                        ______________________________________                                        Examples          1        2        3                                         ______________________________________                                        Final Product                                                                 Yield, Kg Pol/g Cat                                                                             11       16.3     9.9                                       Comonomer, wt. %  24.6     22.7     29.0                                      Bipolymer (b)+(c), wt. %                                                                        70       67       71.8                                      Intrinsic Visc., dl/g                                                                           2.05     2.3      2.34                                      Xyl. Sol. (S.sub.f), wt. %                                                                      63.4     60.5     63.5                                      Ethylene Xyl. Sol., wt. %                                                                       30.2     27.0     34.8                                      (C.sub.f)                                                                     Intrinsic Vis. Xyl. Sol.                                                                        1.83     2.02     2.12                                      I.V..sub.Sf, dl/g                                                             Fraction (b), wt. %                                                                             9.45     9.37     11.34                                     Fraction (c), wt. %                                                                             60.55    57.63    60.46                                     Ethylene frac. (b), wt. %                                                                       51.9     57.1     53.7                                      Ethylene frac. (c), wt. %                                                                       31.1     27.6     35.7                                      Intrinsic Vis. frac. (c)                                                                        1.86     2.05     2.18                                      I.V..sup.c), dl/g                                                             Melt Index, °C.                                                                          150      147      145                                       Flexural modulus, MPa                                                                           30       77       82                                        R.C.I. IZOD at -50° C., J/m                                                              NB.sup.1 NB       NB                                        Shore D hardness  24       25       20                                        Tension Set at 75%, %                                                                           41       28       36                                        Tensile strength, MPa                                                                           13.8     15.8     15.4                                      Tensile strength at yield,                                                                      5.0      5.8      4.6                                       MPa                                                                           Elongation at break, %                                                                          517      925      940                                       Haze, %           31       34       35                                        Vitreous transition.sup.2, °C.                                                           -25(P)   -23(P)   -28(P)                                                      -75      -119     -81                                                         -128     -121     -125                                      ______________________________________                                         .sup.1 NB = no break                                                          .sup.2 (P) = main peak                                                   

EXAMPLE 4

This example illustrates a cast film material of a blend of the presentinvention and a method for preparing the same.

A cast film of the blend of the present invention containing 1) 75% of aheterophasic olefin polymer material composition, produced according tothe method of example 2, except that, component 1 (a) is present in anamount of about 37% and 63% is component 1 (b) +(c), visbroken to 30 MFRfrom an initial, as polymerized MFR of 0.8; and 2) 25% of DOWLEX 2045, alinear low density polyethylene containing octene-1, having a melt indexof 1.0 g/10 min and a density of 0.92, is prepared by charging the blendinto an extruder, extruding it through a flat film die and quenchingonto a chill roll to produce a film of 0.8 mil thickness using thefollowing equipment and processing conditions:

Screw design: Compression ratio 4:1 to 2:1. Feed zone depth: 0.435 to0.490" (3.5" extruder with 3.5:1 compression ratio) Metering zone depth:0.125 to 0.140" for 3.5" extruder.

Die: Conventional center-fed coathanger manifold.

Extruder operating conditions:

Melt temperature: 400°-460° F.

Extruder Barrel: 350°-420° F. from zone 1 to zone

Adapter and die temperatures: 420° F.

Control 1

A cast film material of a heterophasic olefin polymer materialcomposition,obtained by sequential polymerization in at least twostages, containing 37% of a propylene-ethylene copolymer, (96.7:3.3 wt.ratio of polymerized units), and 63% of an ethylene-propylene copolymer,(29:71 wt. ratio of polymerized units), visbroken to 30 MFR from aninitial, as polymerized MFR of 0.8, prepared according to the proceduredescribed above.

                                      TABLE 2                                     __________________________________________________________________________             CONTROL          EXAMPLE 4                                           ELONGATION                                                                             % DEFORM.                                                                             % RECOVERY                                                                             % DEFORM.                                                                             % RECOVERY                                  __________________________________________________________________________    10%       4.1    95.9      5.3    94.7                                        25%      11.8    88.2     11.8    99.2                                        50%      17.0    83.0     15.7    84.4                                        75%      20.2    79.8     19.1    81.0                                        __________________________________________________________________________

As demonstrated in Table 2 above, at 10% and 25% elongation very littledifference is seen in the % deformation and recovery between example 4andcontrol. However, at elongations of 50% and 75%, in the blend of thepresent invention, example 4, the percent deformation decreases and thepercent recovery increases, whereas the percent deformation increasesand the percent recovery decreases in the composition of the control,which does not contain LLDPE.

Illustrated in Table 3 is the tear strength and impact strength of castfilm material of the blend of the present invention, Example 4, and thecontrol composition, which does not contain LLDPE.

                  TABLE 3                                                         ______________________________________                                        PROPERTIES       CONTROL     EXAMPLE 4                                        ______________________________________                                        Film Thickness, mil                                                                            2.2         2.2                                              Elmendorf Tear Strength, g                                                                     430/610     440/790                                          (MD/CD)                                                                       Dart Impact Strength, g                                                                        520         740                                              ______________________________________                                    

As demonstrated in Table 3, a significant increase in the tear andimpact strength of the blend of the invention is obtained, as comparedto the control, which does not contain LLDPE.

Various types of film materials of conventional thickness and thin filmsless than 20 mils thick to as thin as about 0.5 mils can be preparedusingthe heterophasic olefin polymer composition described herein aswell as heavy film materials, typically referred to as sheets, from 20to 100 milsthick. For example, it can be used to prepare cast films,uniaxially and biaxially oriented films and extruded or calendaredsheets. In addition a layer comprising the heterophasic olefin polymercomposition can be applied to, e.g. by lamination, extrusion coating orcoextrusion techniques, at least one surface of a thermoplastic filmmaterial or a metallic sheet or foil substrate or a woven or non-wovenmaterial.

Typical thermoplastic materials include crystalline homopolymers of aC₂₋₁₀ alpha-olefin monomer, such as propylene or ethylene, or copolymersof propylene with ethylene or with a C₄₋₁₀ alpha-olefin monomers or ofpropylene with both ethylene and a C₄₋₁₀ alpha-olefin monomers, providedthat, when the comohomer is ethylene, the maximum polymerized ethylenecontent is about 10%, preferably about 4%, and when the comohomer is aC₄₋₁₀ olefin, the maximum polymerized content thereof is about 20%,preferably about 16%, and when both ethylene and an alpha-olefin areused the maximum polymerized content of both is 30%, preferably 20%, aswell as polyesters, polyamides, ethylene-vinyl alcohol copolymers andethylene-vinyl acetate copolymers. Aluminum is a suitable metallicsubstrate. In addition, film materials can be prepared from blends offrom about 5 to 45% of the present invention described herein with fromabout 95 to 55% of a crystalline homopolymer of a C₂₋₁₀ alpha-olefinmonomer or copolymer of propylene with ethylene or with a C₄₋₁₀alpha-olefin monomer or of propylene, ethylene and a C₄₋₁₀alpha-olefinmonomer, said copolymer having the maximum polymerized contentofethylene or alpha-olefin or both as described in the precedingparagraph. Preferably, the amount of the blend of the present inventioninsuch blends is from 10 to 30%.

Other features, advantages and embodiments of the invention disclosedherein will be readily apparent to those exercising ordinary skill afterreading the foregoing disclosures. In this regard, while specificembodiments of the invention have been described in considerable detail,variations and modifications of these embodiments can be effectedwithout departing from the spirit and scope of the invention asdescribed and claimed.

What is claimed is:
 1. A film or sheet material comprising a blend of 1)from 95 to 60%, by weight of a heterophasic olefin polymer compositionprepared by polymerization in at least two stages which is comprisedof(a) from about 10 to 50 parts of a propylene homopolymer having anisotactic index greater than 80, or a copolymer selected from the groupconsisting of (i) propylene and ethylene, (ii) propylene, ethylene and aCH₂ ═CHR alpha-olefin, where R is a C2-8 straight or branched alkyl, and(iii) propylene and an alpha-olefin as defined in (ii), said copolymercontaining over 80% propylene and having an isotactic index greater than80; (b) from about 5 to 20 parts of a semi-crystalline, essentiallylinear copolymer fraction having a crystallinity of about 20 to 60%wherein the copolymer is selected from the group consisting of (i)ethylene and propylene containing over 55% ethylene, (ii) ethylene,propylene, and an alpha-olefin as defined in (a) (ii) containing from 1to 10% of the alpha-olefin and over 55% of both ethylene andalpha-olefin, and (iii) ethylene and an alpha-olefin as defined in (a)(ii) containing over 55% of said alpha-olefin, which copolymer isinsoluble in xylene at room or ambient temperature; and (c) from about40 to 80 parts of a copolymer fraction wherein the copolymer is selectedfrom the group consisting of (i) ethylene and propylene containing from20% to less than 40% ethylene, (ii) ethylene, propylene, and analpha-olefin as defined in (a) (ii) wherein the alpha-olefin is presentin an amount of 1 to 10% and the amount of ethylene and alpha-olefinpresent is from 20% to less than 40%, and (iii) ethylene and analpha-olefin as defined in (a) (ii) containing from 20% to less than 40%of said alpha-olefin, and optionally with 0.5 to 10% of a diene, saidcopolymer fraction being soluble in xylene at ambient temperature, andhaving an intrinsic viscosity of from 1.5 to 4.0 dl/g; with the total ofthe (b) and (c) fractions, based on the total olefin polymercomposition, being from about 50% to 90%, and the weight ratio of(b)/(c) being less than 0.4; and 2) from 5 to 40%, by weight of acopolymer of ethylene with a CH₂ ═CHR alpha-olefin, where R is a C₁₋₈straight or branched alkyl, having a density of from 0.890 to 0.940g/cm³.
 2. The material of claim 1 wherein (a) is a copolymer ofpropylene and ethylene containing from 90 to 98% propylene.
 3. Thematerial of claim 1 wherein (c) is a copolymer of propylene and ethylenecontaining from 20 to 38% ethylene.
 4. The material of claim 1 whereincomponent (2) is an ethylene copolymer containing an octene-1 comonomer.5. The material of claim 4 wherein said ethylene copolymer has a densityof from 0.890 to 0.927 g/cm³.
 6. The material of claim 1 wherein saidethylene copolymer of component is a linear low density polyethylene. 7.The material of claim 1 wherein component 1) is present in an amount offrom 90 to 75% and component 2) is present in an amount of from 10 to25%.
 8. The material of claim 2 wherein the total content ofcopolymerized ethylene is from 15% to 35% by weight.
 9. The material ofclaim 3 wherein the total content of copolymerized ethylene is from 15%to 35% by weight.